A low-cost freezing technology can safeguard the genetic diversity of indigenous chickens in low- and middle-income countries, a study has found.

Chicks that have been born from surrogate chickens that received formerly frozen reproductive cells extracted from embryos, derived entirely from donor chickens.

The cryopreservation method could help preserve the 1,600 local chicken breeds that are an important source of income for smallholder farmers in tropical countries. It could also help secure poultry genes from indigenous breeds for efforts to develop birds with climate resilience or disease resistance and to ensure food production.

"This simple, low-cost and low-tech biobanking method will be beneficial to poultry breeders worldwide, big or small. It will reduce the cost of maintaining livestock for breeding, and will benefit the welfare of chickens by reducing the number of birds in research facilities," said Dr. Tuanjun Hu, The Roslin Institute and CTLGH.

Simple method

A team from the Centre for Tropical Livestock Genetics and Health (CTLGH) and the Roslin Institute, with their commercial partner Cobb-Europe, validated a simple technique in which chicken reproductive organs were extracted from embryos, pooled by sex and frozen.

After being thawed, the reproductive cells were injected into sterile surrogate embryos. Male reproductive cells were injected into male embryos, and female cells into female embryos.

Research using fluorescent proteins to label the donors’ cells and a method to control the reproductive genes carried by both parents – known as Sire Dam Surrogate mating – demonstrated that chicks were derived entirely from their donor parents.

Freezing the entire reproductive organ is more effective than freezing separated reproductive cells, experiments showed.

While cryopreservation of reproductive cells from adult livestock is routine, it is problematic in poultry, and in vitro alternatives are technically demanding and expensive. This simple technique does not require cells to be created in vitro in the laboratory, making it easier and cheaper to preserve chickens, benefiting both commercial and smallholder farmers, according to Dr Mike McGrew, the Roslin Institute and Programme Leader at CTLGH.

"The chicken is a key animal for millions of smallholder farmers in low- and middle-income countries. This simple and low-cost method, developed through a CTLGH collaboration between Roslin, ILRI and Cobb-Europe, will enable conservation of chicken diversity, to ensure that farmers can breed birds that are resilient to extreme climates, and a reliable source of food and income for farming families," said Professor Appolinaire Djikeng, CTLGH Director.

The study is published in the journal eLife and was funded by the Bill & Melinda Gates Foundation, the UK Foreign, Commonwealth and Development Office under the auspices of CTLGH, and the National Centre for the Replacement, Refinement, and Reduction of Animals in Research.